Abstract: At the end of 2019, the virus causing the coronavirus disease (COVID-19) was identified in Wuhan, China, wich has affected more than 1.5 million people worldwide. The easy transmission by aerosols and direct contact, represents a challenge for personnel who manipulate the airway of these patients. We present the case of a 33-year-old woman diagnosed with COVID-19 pneumonia, under prolonged intubation scheduled for tracheostomy. The aim of this report is to review the anesthetic considerations during this procedure in this group of patients, in order to reduce the risk of contagion in health personnel.

Resumen: A finales de 2019 se identificó en Wuhan, una provincia de China, el virus causante de la enfermedad por coronavirus (COVID-19), el cual ha afectado a más de 1.5 millones de personas en todo el mundo. La fácil transmisión por aerosoles y contacto directo representa un reto para el personal que manipula la vía aérea de estos pacientes. Presentamos el caso de una mujer de 33 años con diagnóstico de neumonía por COVID-19, a quien se realizó una traqueostomía percutánea por intubación prolongada. El objetivo de esta publicación es revisar las consideraciones anestésicas durante este procedimiento en este grupo de pacientes para lograr disminuir el riesgo de contagio en el personal de salud.

High energy ball milling and sonofragmentation were used successfully to reduce the crystallite size of calcium carbonate extracted from the eggshell. The ceramic was milled using either deionized water or stearic acid and then subjected to a subsequent size reduction by means of a tip horn. The thermal degradation of particles was influenced by the presence of stearic acid in milling process because it acts as a protective layer around eggshell particles. It was found that the reduction in crystallite size diminishes the degradation temperature and the presence of the surfactant may lead to a change in particle shape by trough a superplasticity phenomenon. Tubes, fibers and a rectangular prism were observed in Transmission Electron Microscopy.

Abstract Over five million tons of chicken feathers (CF) are generated all over the world by the poultry industry, with an immense potential to exploit. Keratin is an abundant protein found in chicken feathers that offers excellent thermal properties and it is durable, insoluble in organic solvents and chemically unreactive. Elastomers are materials with a wide application range, for instance, adhesives, shoe soles, plastic modifiers, tire industry, sealants, among others. However, it is necessary to improve their properties and mechanical performance at elevated temperatures. A good path to do so is to combine the elastomer with CF to obtain materials with enhanced properties. In present work, a composite based on styrene-butadiene (SB) elastomer and CF was prepared by means of melt mixing. Composites were characterized by FTIR, DSC, DMA and X ray diffraction techniques. The results show that there is an increase in stiffness of SB/CF composites compared with pure elastomer.

Resumen Esta investigación fue enfocada en la dispersión de una arcilla de marca comercial Cloisite 10A en PET reciclado (RPET) para mejorar las propiedades del polímero reciclado que se perdieron en el reprocesamiento de los materiales, específicamente durante la extrusión. Diferentes mezclas de RPET/Cloisite 10A fueron preparadas en un extrusor monohusillo. Las mezclas obtenidas fueron reprocesadas en un extrusor monohusillo tipo reómetro y pasadas a traves de un dado capilar en altos esfuerzos de corte para para incrementar la dispersión de la arcilla en la matriz polimérica. Los resultados muestran degradación física de los materiales. Difracción de rayos X (XRD) indica exfoliación de la arcilla con bajas concentraciones. Además, los resultados reológicos muestran decremento en la viscosidad con incremento de la concentración de la arcilla en las mezclas. Microscopia electrónica de barrido (SEM) revela baja dispersión de la arcilla con incremento de la concentración.

Abstract This research focuses on clay dispersion of commercial Cloisite 10A in recycled PET (RPET) to improve the properties of recycled polymer lost in the reprocessing of materials, specifically during extrusion. Varying mixtures of RPET/Cloisite 10A were prepared in a single screw extruder. The mixtures obtained were reprocessed in capillary rheometer-type single screw extruder and passed through a capillary die, at high shear stress to increase the dispersion of clay in the polymer matrix. Results show physical degradation of materials. X-ray diffraction (XRD) indicated exfoliation of clay with low concentrations. Furthermore, rheology results show that viscosity rate decreases with increase in clay concentration in the mixtures. Scanning electron microscopy (SEM) reveals low dispersion of clay with an increase of concentration.

<p>Curing is an important process in adhesive formulation, but scant reports on the study of the kinetics of curing in adhesive are currently available, particularly for formulations including styrene-butadiene copolymers. The focus of the present work was to thermodynamically quantify the curing reaction in pressure-sensitive adhesives (PSA) obtained from styrene-butadiene copolymers, the effect of dicumyl peroxide (DCP) ratio, which acts as a crosslinking agent, and also evaluate the effect of two reactive adhesive resins, sylvalite and piccolyte. Kinetic parameters were determined by differential scanning calorimetry (DSC) in an isothermic and dynamic mode, gel content was determined as was swelling degree, given these characteristics can be associated with the curing reaction. The kinetic study showed the curing reaction was first order, according to the Ozawa and Kissinger equation. Resins have affinity to BR segment, while in the case of sylvalite and piccolyte to the PS segment, varying behavior with dicumyl peroxide in the adhesive mixture. Lower swelling values were associated with an increase in crosslinking, indicative a curing reaction took place, and the gel content test was used to corroborate the results.</p>

The mixture of synthetic and natural materials yields a material with improved physical-chemical properties. One way of obtaining this kind of material is through graft copolymerization. Some natural materials have been used in graft copolymerization with synthetic monomers. In this work, graft copolymerization of butyl acrylate (BA) onto starch using a redox initiator system was carried out. The graft yield was evaluated for different reaction conditions. The graft copolymer was characterized by infrared spectroscopy, thermal analysis and scanning electron microscopy (SEM).

Blending of two or even more immiscible polymers is a very useful method to obtain new polymeric materials with ordered and tailored properties. Thermoplastic elastomers (TPE's) are interesting materials for various applications, including the automotive industry, due to their excellent balance between processability and physical properties, especially using hydrogenated styrene-butadiene copolymer. In the present work, two structures of styrene-ethylene/buthylene-styrene (SEBS) triblock copolymer (linear and radial) were blended with polypropylene (PP) using a process aid oil. Three different SEBS-PP ratios were evaluated. Phase behavior was studied by means of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and Scanning electron microscopy (SEM), which confirmed the formation of a single phase material. PP crystallinity was affected by SEBS structure causing a lamellar thinning of crystals. The SEM analysis shows that radial and linear structures of SEBS have different morphology.